Blowroom and preparatory spinning facilities function to continuously produce slivers which, as far as possible, are not subject to any variations in any of their properties, and which correspond as far as possible to predetermined set-values. This problem can be optimally solved only by continuously monitoring and correcting the manufacturing process at different places in the manufacturing process sequence. Accordingly, data concerning the properties of the sliver at different places in the processing process must be made available.
The properties of a particular sliver prepared in a preparatory spinning facility depends upon a number of variables. These variables include the properties of the fibers, the nature and stage of the processing of the fiber and the ambient conditions. Thus, the properties of a specific sliver are determined by a set of parameter values.
Important sliver parameters include the origin of the fiber; the quantity of textile material per sliver unit length; the mutual position of the fibers that form the sliver; and the quantity, nature, size and form of foreign material and its distribution in the sliver. Important fiber parameters include the fineness and fineness distribution of the fibers forming the sliver; the length and length distribution of the fibers forming the sliver; the surface properties and forms of the fibers forming the sliver (i.e., degree of maturity); and, the fiber color. Important process parameters include the textile material or sliver material blend; the speed at which the sliver is formed; and, the tension of the sliver. Important ambient parameters include the humidity of the fibers and the environment; and, the temperature of the fibers and the environment.
Some of the above noted parameters must be kept constant per unit of time, as, for example, the ambient parameters. On the other hand, the staple length of the sliver is determined in several ways, such as, for example, using laboratory (i.e. static) methods, which are introduced as values into the process. The method under discussion here comprises a dynamic measuring method.
Two slivers have the same qualities if all the parameter values for both slivers are identical. Certain conclusions regarding the difference between two slivers, with respect to one parameter, can be made if all the other parameter values are the same, or, alternatively, if it is known whether a parameter value, is dependent upon another parameter value and if so, how. There are numerous standardized laboratory investigative methods for such comparison purposes. Such investigations are usually carried out under standardized ambient conditions and usually with standardized quantities and standardized arrangements of fibers in a static state. In this way, all of the above-mentioned processing, ambient and most of the sliver parameters are kept constant, so that it is possible to compare fibers, slivers and spun products.
The following measuring methods are known for continuously measuring the mass or fiber density of slivers:
European Patents 78,393 and 192,835 disclose measuring the mass of a sliver by mechanically compressing the sliver between two rollers. One of the rollers is driven and non-displaceable, while the second roller is entrained and is displaceable parallel to its own axis. The displaceable roller exerts a constant force on the sliver and is displaced from its rest position in accordance with the compressibility of the sliver. The deflection of the entrained roller is then measured. The deflection of the roller is mainly upon the fiber material and is a function of the quantity of fiber substance.
German Offenlegungsschrift 2,323,729 and Swiss Patent 629,546 disclose compressing a sliver in a trumpet in order to measure the density of the fiber. Dynamic pressure formed by air being squeezed out of the sliver is then measured. A variant of this measuring method comprises blowing an airstream having a constant pressure and constant flow through the sliver, perpendicularly to its direction of movement, and measuring a pressure drop over the sliver. In both cases, aerodynamic resistance of the sliver to the airstream is measured. The results of this type of measurement is primarily dependent upon the quantity of material, the fiber fineness, the fiber orientation in the sliver, the surface and shape of the fibers and the sliver speed.
Sliver measuring methods suitable for continuous investigations depend upon several parameters. However, in contrast to the non-continuous laboratory methods, it is not possible to eliminate the influence of several parameters by means of standard conditions (i.e., standardized preset conditions and/or invariability of some conditions over time). For example, ambient conditions and processing parameters may vary over time and at various points of the sliver production process in the blowroom and preparatory spinning facility. In addition, the sliver parameters and the fiber parameters may also vary. Since, however, the results of the continuous monitoring of the sliver properties can be used for instituting corrective action and to activate alarms only if they can be reduced to individual parameters, it is important to find ways and means for breaking up the measurement results into individual and independent parameters. Since short-term and long-term fluctuations in the properties of slivers and fibers may lead to different corrective actions or alarms, it is important to separate these two types of fluctuations.
Practically all continuously obtained measurement results depend upon sliver humidity. These results cannot be compared with set values, unless they have previously been reduced to standard conditions. Controlling a flock feed and drafting process requires having data concerning material quantity on the sliver, which is produced by feeding and drafting, and this is necessary independently of the other fiber parameters. For example, controlling a bale opening and blenders requires having data relating to the fibers, irrespective of how much material the sliver under measurement contains at the time of measurement.